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| author | Waiman Long <longman@redhat.com> | 2018-07-18 00:59:27 +0300 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2018-08-06 18:59:04 +0300 |
| commit | 3553ae5690a84a5baae5baa329467b3df2d99f72 (patch) | |
| tree | 336d0d26cfb9af7c6c0ef2c9ce7d835e2fcf1e7a | |
| parent | 450917b654c12075bd2b07d1e375dfed1bc9ca1e (diff) | |
| download | linux-3553ae5690a84a5baae5baa329467b3df2d99f72.tar.xz | |
x86/kvm: Don't use pvqspinlock code if only 1 vCPU
On a VM with only 1 vCPU, the locking fast path will always be
successful. In this case, there is no need to use the the PV qspinlock
code which has higher overhead on the unlock side than the native
qspinlock code.
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
| -rw-r--r-- | arch/x86/kernel/kvm.c | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c index 5b2300b818af..575c9a51e6ba 100644 --- a/arch/x86/kernel/kvm.c +++ b/arch/x86/kernel/kvm.c @@ -748,6 +748,10 @@ void __init kvm_spinlock_init(void) if (kvm_para_has_hint(KVM_HINTS_REALTIME)) return; + /* Don't use the pvqspinlock code if there is only 1 vCPU. */ + if (num_possible_cpus() == 1) + return; + __pv_init_lock_hash(); pv_lock_ops.queued_spin_lock_slowpath = __pv_queued_spin_lock_slowpath; pv_lock_ops.queued_spin_unlock = PV_CALLEE_SAVE(__pv_queued_spin_unlock); |